Flame retardant polyester compositions

ABSTRACT

A halogen-free, flame retardant polyester composition comprises, based on the total composition,  
     (a) A poly(ethylene terephthalate) with a molecular weight of at least 50,000 or a blend of poly(ethylene terephthalate) with another polyester, taking into account that the ratio poly(ethylene terephthalate)/other polyester should be at least 55/45.  
     (b) A combination of at least one N-containing compound, selected from the group of triazine, guanidine, or (iso)cyanurate compounds, and at least one P-containing compound, selected from the group of BPA-diphosphates or phosphoramides with the proviso that the ratio of the total amount of P- and N-containing compounds over the total polyester amount should be between 0.3 and 0.6 and the ratio of the P-containing compound over the N-containing compound should be higher than 0.8.  
     (c) An anti-dripping agent in an amount of 0.01-2 weight percent of the total composition.  
     (d) A reinforcing filler in an amount of 040 weight percent of the total composition.

FIELD OF THE INVENTION

[0001] This invention relates to thermoplastic polyester compositions,and in particular to halogen-free, flame retardant thermoplasticpolyester compositions.

BACKGROUND OF THE INVENTION

[0002] Thermoplastic polyester compositions, such as poly(alkyleneterephthalates) have valuable characteristics including strength,toughness, high gloss and solvent resistance. Polyesters therefore haveutility as materials for a wide range of applications, from automotiveparts to electric and electronic appliances. Because of their wide use,particularly in electronic applications, it is desirable to provideflame retardancy to polyesters. One particular set of conditionscommonly accepted and used as a standard for flame retardancy is thatwhich is set forth in Underwriter's Laboratories, Inc. Bulletin 94 whichproscribes certain conditions by which material are rated forself-extinguishing characteristics. Another set of conditions commonlyaccepted and used (especially in Europe) as a standard for flameretardancy is the so-called Glow Wire Test (GWT), the Internationalstandard IEC 695-2-1/2.

[0003] Numerous flame retarding agents for polyesters are known, butmany contain halogens, usually bromine. Halogenated flame retardantagents are however less desirable because of the increasing demand forecological friendly ingredients. Alternative flame retarding agents havetherefore been developed, based on for instance Nitrogen and/orPhosphorus compounds. A general disadvantage of these flame retardantingredients in polyesters is the negative effect on properties as impactand color stability upon oven aging. Several N-containing compounds,combined with P-containing compounds have been described as flameretardants for polyesters. JP 03-281652 to Mitsubishi Petrochemical, forexample, discloses FR polyester compositions comprising 100 parts of apolyester resin, 30-250 parts of a filler, 5-50 parts of melaminecyanurate, and 5-50 parts of a P-containing FR compound. JP 06-157880 toAkzo Kashima, Mitsubishi Petrochemical, describes a polyester (100parts) with 30-250 pts of a filler, 5-50 parts of melamine cyanurate and5-50 parts of an aromatic phosphate. JP11209587 to Kaneka discloses apolyester composition with a) 20-59% Glass and mineral filler in a ratioof 3/2-1/4, b) melamine cyanurate and c) 15-32% P-compound withP-compound/Melamine cyanurate ratio of 1/1-1/3, and d) 0.01-2% Fluororesin.

[0004] Above mentioned literature/patents are suitable for the intendedflame-retardant properties, but none of them describes potentiallimitations of the claimed composition ingredients and the claimedamounts for practical use. Not only good flame retardancy is needed buta combination of good flame retardant properties with good ductility andcolor stability upon oven aging. The herewith described inventionovercomes the described deficiencies.

BRIEF SUMMARY OF THE INVENTION

[0005] Non-halogenated flame retardants for polyesters, based on N- andP-containing compounds, are described in the literature. Although goodFR-properties can be obtained upon high enough amounts of theFR-ingredients, the materials lack good mechanical properties as impactand/or have insufficient color stability upon heat aging. Desirableenhanced properties and deficiencies can be overcome by the properchoice of the P-compound and the right amounts of N- and P-compounds inrelation which each other and in relation with the type and amount ofthe present polyester. Good balance of ductility, flame retardancy andcolor stability upon oven aging can be obtained by a flame retardantpolyester composition comprising, based on the total composition,

[0006] (a) A poly(ethylene terephthalate) with a molecular weight of atleast 50,000 or a blend of poly(ethylene terephthalate) with anotherpolyester, taking into account that the ratio poly(ethyleneterephthalate)/other polyester should be at least 55/45.

[0007] (b) A combination of at least one N-containing compound, selectedfrom the group of triazine, guanidine, or (iso)cyanurate compounds, andat least one P-containing compound, selected from the group ofBPA-diphosphates or phosphoramides with the proviso that the ratio ofthe total amount of P- and N-containing compounds over the totalpolyester amount should be between 0.3 and 0.6 and the ratio of theP-containing compound over the N-containing compound should be higherthan 0.8.

[0008] (c) An anti-dripping agent in an amount of 0.01-2 weight percentof the total composition.

[0009] (d) A reinforcing filler in an amount of 040 weight percent ofthe total composition.

DETAILED DESCRIPTION OF THE INVENTION

[0010] A halogen-free, flame retardant polyester composition comprises,based on the total composition,

[0011] (a) A poly(ethylene terephthalate) with a molecular weight of atleast 50,000 or a blend of poly(ethylene terephthalate) with anotherpolyester, taking into account that the ratio poly(ethyleneterephthalate)/other polyester should be at least 55/45

[0012] (b) A combination of at least one N-containing compound, selectedfrom the group of triazine, guanidine, or (iso)cyanurate compounds, andat least one P-containing compound, selected from the group ofBPA-diphosphates or phosphoramides with the proviso that the ratio ofthe total amount of P- and N-containing compounds over the totalpolyester amount should be between 0.3 and 0.6 and the ratio of theP-containing compound over the N-containing compound should be higherthan 0.8.

[0013] (c) An anti-dripping agent in an amount of 0.01-2 weight percentof the total composition.

[0014] (d) A reinforcing filler in an amount of 0-40 weight percent ofthe total composition.

[0015] The flame retardant polyester composition includes a flameretarding quantity of one or a mixture of nitrogen-containing compounds,selected from the group of triazine, guanidine, or (iso)cyanuratecompounds. Examples of such compounds are the 1,3,5-triazine compoundsas for instance 2,4,6-triamine-1,3,5-triazine (melamine), melam, melem,melon, ammeline, ammelide, 2-ureidomelamine, acetoguanamine,benzoguanamine, diaminephenyltriazine or mixtures thereof. Especiallysalts/adducts of these compounds with (iso)cyanuric acid (as eg melaminecyanurate), boric acid, and/or phosphoric acid (including the so calledmelamine polyphosphate) can be used in the composition. Preferredcompounds include the cyanuric acid derivatives of1,3,5-triazine-compounds as melamine cyanurate.

[0016] The nitrogen-containing compounds are used in combination withone or more phosphorous-containing compounds as described below, sincethe combination appears to impart better flame retardant properties thanwhere either component is used alone.

[0017] A suitable class of phosphorous compounds is the class ofdiphosphates of the general structure (OR1)(OR2)P(═O)—OXO—P(═O)(OR3(OR4)(optionally including some oligomeric higher phosphates), for instancemade out of POCl3, a diphenol compound HO—X—OH with X is a group with atleast 2 aryl unit (such as bisphenol A), and mono-hydroxy compound(s)ROH (R1, R2, R3, R4 might be equal or different), such as phenol. Othersuitable phosphorus compounds are phosphoramides such as tetraxylylpiperazine diphosphoramide.

[0018] The phosphoramides have the following general structure:

[0019] wherein R1 is an amine residue, and R2 and R3 are independentlyan alkoxy residue, aryloxy residue, aryloxy residue containing at leastone alkyl or one halogen substitution or mixture thereof, or amineresidue. It is preferred that the phosphoramide have a glass transitionpoint of at least about 0° C., preferably of at least about 10° C., andmost preferably of at least about 20° C.

[0020] Another phosphoramide comprises a phosphoramide having a glasstransition temperature of at least about 0° C., preferably of at leastabout 10° C., and most preferably of at least about 20° C., of theformula:

[0021] wherein each A is independently phenyl, 2,6-dimethylphenyl, or2,4,6-trimethylphenyl.

[0022] The composition may further optionally comprise various fillersand other additives known in the art, particular glass fibers in anamount of up to about 40 weight percent, and 0.01 to about 2.0 weightpercent of at least one anti-dripping agent which retards the tendencyof the composition to drip when subjected to burning conditions.

[0023] Suitable polyesters that can be blend with the used poly(ethyleneterephthalate) include those derived from an aliphatic or cycloaliphaticdiol, or mixtures thereof, containing from 2 to about 10 carbon atomsand at least one aromatic dicarboxylic acid. Preferred polyesters arederived from an aliphatic diol and an aromatic dicarboxylic acid havingrepeating units of the following general formula:

[0024] wherein n is an integer of from 2 to 6, and R is a C6-C20 arylradical comprising a decarboxylated residue derived from an aromaticdicarboxylic acid.

[0025] Examples of aromatic dicarboxylic acids represented by thedecarboxylated residue R are isophthalic or terephthalic acid,1,2-di(p-carboxyphenyl)ethane, 4,4′-dicarboxydiphenyl ether, 4,4′bisbenzoic acid, and mixtures thereof. All of these acids contain atleast one aromatic nucleus. Acids containing fused rings can also bepresent, such as in 1,4-1,5- or 2,6-naphthalene dicarboxylic acids. Thepreferred dicarboxylic acids are terephthalic acid, isophthalic acid,naphthalene dicarboxylic acid or a mixtures thereof.

[0026] The aliphatic polyols include glycols, such as propylene glycol,butanediol, hydroquinone, resorcinol, trimethylene glycol,2-methyl-1,3propane glycol, hexamethylene glycol, decamethylene glycol,cyclohexane dimethanol, or neopentylene glycol.

[0027] Also contemplated herein are the above polyesters with minoramounts, e.g., from about 0.5 to about 30 percent by weight, of unitsderived from aliphatic acids and/or aliphatic polyols to formcopolyesters. The aliphatic polyols include glycols, such aspoly(ethylene glycol). Such polyesters can be made following theteachings of, for example, U.S. Pat. Nos. 2,465,319 and 3,047,539.

[0028] The most preferred polyesters are poly(ethylene terephthalate)(“PET”) as main polyester, poly(1,4-butylene terephthalate), (“PBT”),and poly(propylene terephthalate) (“PPTI”). A preferred PBT resin is oneobtained by polymerizing a glycol component at least 70 mole %,preferably at least 80 mole %, of which consists of tetramethyleneglycol and an acid component at least 70 mole %, preferably at least 80mole %, of which consists of terephthalic acid, and polyester-formingderivatives therefore. The preferred glycol component can contain notmore than 30 mole %, preferably not more than 20 mole %, of anotherglycol, such as ethylene glycol, trimethylene glycol,2-methyl-1,3-propane glycol, hexamethylene glycol, decamethylene glycol,cyclohexane dimethanol, or neopentylene glycol. The preferred acidcomponent can contain not more than 30 mole %, preferably not more than20 mole %, of another acid such as isophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalene dicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 4,4′-diphenyl dicarboxylic acid, 4,4′-diphenoxyethanedicarboxylic acid, p-hydroxy benzoic acid, sebacic acid, adipic acid andpolyester-forming derivatives thereof.

[0029] Block copolyester resin components are also useful, and can beprepared by the transesterification of (a) straight or branched chainpoly(1,2ethylene terephthalate) and (b) a copolyester of a linearaliphatic dicarboxylic acid and, optionally, an aromatic dibasic acidsuch as terephthalic or isophthalic acid with one or more straight orbranched chain dihydric aliphatic glycols. Especially useful when highmelt strength is important are branched high melt viscosity resins,which include a small amount of e.g., up to 5 mole percent based on theterephthalate units, of a branching component containing at least threeester forming groups. The branching component can be one which providesbranching in the acid unit portion of the polyester, or in the glycolunit portion, or it can be hybrid. Illustrative of such branchingcomponents are tri- or tetracarboxylic acids, such as trimesic acid,pyromellitic acid, and lower alkyl esters thereof, and the like, orpreferably, polyols, and especially preferably, tetrols, such aspentaerythritol, triols, such as trimethylolpropane; or dihydroxycarboxylic acids and hydroxydicarboxylic acids and derivatives, such asdimethyl hydroxyterephthalate, and the like. The branchedpoly(1,4-butylene terephthalate) resins and their preparation aredescribed in Borman, U.S. Pat. No. 3,953,404, incorporated herein byreference. In addition to terephthalic acid units, small amounts, e.g.,from 0.5 to 15 percent by weight of other aromatic dicarboxylic acids,such as isophthalic acid or naphthalene dicarboxylic acid, or aliphaticdicarboxylic acids, such as adipic acid, can also be present, as well asa minor amount of diol component other than that derived from1,4-butanediol, such as ethylene glycol or cyclohexylenedimethanol,etc., as well as minor amounts of trifunctional, or higher, branchingcomponents, e.g., pentaerythritol, trimethyl trimesate, and the like.

[0030] Fillers and other additives known in the art may be employed toachieve the desired processing and physical characteristics of the flameretardant polyester composition. Typically, such stabilizers are used ata level of about 0.01-10 weight percent and preferably at a level ofabout 0.05-2 weight percent. The preferred stabilizers include aneffective amount of an acidic phosphate salt; an acid, alkyl, aryl ormixed phosphite having at least one hydrogen or alkyl group; a Group IBor Group IIB metal phosphate salt; a phosphorous oxo acid, a metal acidpyrophosphate or a mixture thereof. The acidic phosphate salts includesodium dihydrogen phosphate, mono zinc phosphate, potassium hydrogenphosphate, calcium dihydrogen phosphate and the like. The phosphites maybe of the formula:

[0031] wherein R1, R2, and R3 are independently selected from the groupconsisting of hydrogen, alkyl and aryl with the proviso that at leastone of R1, R2, and R3 is hydrogen or alkyl.

[0032] The phosphate salts of a Group IB or Group IIB metal include zincphosphate, copper phosphate and the like. The phosphorous oxo acidsinclude phosphorous acid, phosphoric acid, polyphosphoric acid orhypophosphorous acid.

[0033] The polyacid pyrophosphates maybe of the formula:

Mz xHyPnO3n+1

[0034] wherein M is a metal, x is a number ranging from 1 to 12 and y isa number ranging 1 to 12, n is a number from 2 to 10, z is a number from1 to 5 and the sum of (xz)+y is equal to n+2.

[0035] Inorganic fillers can impart additional beneficial propertiessuch as thermal stability, increased density, stiffness and texture.Typical inorganic fillers include but are not limited to alumina,amorphous silica, anhydrous aluminum silicates, mica, feldspar, clays,talc, glass flake, glass fibers, glass microspheres, wollastonite, metaloxides such as titanium dioxide, zinc oxide, ground quartz, and t helike. Preferred inorganic fillers include zinc oxide, barium sulfate andfiberglass as well as mixtures of the above. Barium sulfate may be inthe form of the naturally occurring barites or as synthetically derivedbarium sulfate. The particle size may vary, and is preferably from about0.1 to about 50 microns, most preferably from about 1 to about 15microns.

[0036] Where used, fibrous (filamentous) glass can be untreated, butpreferably, it will be treated with silane or titanate coupling agents,e.g. Useful filamentous glass is well known to those skilled in the artand is widely available from a number of manufacturers. For compositionsultimately employed for electrical uses, it is preferred to use fibrousglass filaments comprised of lime-aluminum borosilicate glass that isrelatively soda free, commonly known as “E” glass. However, otherglasses are useful where electrical properties are not so important,e.g., the low soda glass commonly known as “C” glass. The filaments aremade by standard processes, e.g., by steam or air blowing, flame blowingand mechanical pulling. The preferred filaments for plasticreinforcement are made by mechanical pulling. Exemplary filamentdiameters are in the range from about 0.00012 to 0.00075 inch. The glassfilaments may be bundled into fibers and the fibers bundled in turn toyarns, ropes or rovings, or woven into mats, and the like, as isrequired by the particular end use of the composition. In preparing themolding compositions, it is convenient to use the filamentous glass inthe form of chopped strands of from about one-eighth to about 2 incheslong., which usually results in filament lengths between about 0.0005 to0.250 inch in the molded compounds.

[0037] When particulate fillers are present, for example in moldingcompositions, the compositions include from 0 to about 60 weightpercent, preferably from about 10 to about 50 weight percent, and mostpreferably from about 25 to about 40 weight of the total composition.Glass fibers are typically used in quantities from about 0 to about 60weight percent, preferably from about 10 to about 40 weight percent.

[0038] The compositions may also contain one or a mixture of reinforcingfiller. Suitable fillers include silica; silicates such as talc or mica;carbon black; and reinforcing fibers, such as carbon fiber, aramidefiber or glass fiber. Glass fibers may be composed of E-glass or alkalimetal silicate glass and may comprise short, chopped glass fibers with acircular cross section ranging in diameter from about 2×10−4 to 8×10−4inch and about 0.2 to 2 cm in length. Such glass fibers are normallysupplied by the manufacturers with a surface treatment compatible withthe polymer component of the composition, such as a siloxane orpolyurethane sizing. When used in the composition, the reinforcingfiller is normally included at a level of from about 1 to 40 parts byweight, more preferably from about 5 to 35 parts by weight, per 100parts by weight of the total polymer composition.

[0039] The composition may also include one or more anti-dripping agentswhich have the properties of preventing or retarding resin from drippingwhile the resin is subjected to burning conditions. Specific examples ofsuch agents include silicone oils, silica (which also serves as areinforcing filler), asbestos and fibrillating-type offluorine-containing polymers. Examples of fluorine-containing polymersinclude fluorinated polyolefins such as polytetrafluoroethylene,tetrafluoroethylene/hexafluoropropylene copolymers,tetrafluoroethylene/ethylene copolymers, polyvinylidene fluoride andpolychlorotrifluoroethylene. Preferred such fluorine-containing polymershave a melt viscosity at 3500C of about 1.0×104 to 1.0×1014 poises.

[0040] When used, the anti-dripping agent is added to the composition ata level of about 0.05 to 5 parts by weight, more preferably from about0.1 to 4 parts by weight, based on the weight of the total polymercomposition.

[0041] The compositions may also contain other conventional additivesused in polyester polymer compositions such as stabilizers, mold releaseagents, plasticizers and processing aids.

[0042] Other ingredients, such as dyes, pigments, anti-oxidants, and thelike can be added for their conventionally employed purposes.

[0043] The compositions can be prepared by a number of procedures. In anexemplary process, the polyester composition, optional amorphousadditives, impact modifier and filler and/or reinforcing glass is putinto an extrusion compounder with resinous components to produce moldingpellets. The resins and other ingredients are dispersed in a matrix ofthe resin in the process. In another procedure, the ingredients and anyreinforcing glass are mixed with the resins by dry blending, then eitherfluxed on a mill and comminuted, or then are extruded and chopped. Thecomposition and any optional ingredients can also be mixed and directlymolded, e.g., by injection or transfer molding techniques. Preferably,all of the ingredients are freed from as much as water as possible. Inaddition, compounding should be carried out to ensure that the residencetime in the machine is short; the temperature is carefully controlled;the friction heat is utilized; and an intimate blend between the resincomposition and any other ingredients is obtained.

[0044] Preferably, the ingredients are pre-compounded, pelletized andthen molded. Pre-compounding can be carried out in conventionalequipment. For example, after pre-drying the polyester composition (ifnecessary) e.g., for four hours at 120° C., a single screw extruder isfed with a dry blend of the ingredients, the screw employed having along transition section to ensure proper melting. On the other hand, atwin screw extrusion machine, e.g., an extruder with i.e. intermeshingco-rotating screws can be fed with resin and additives at the feed portand reinforcing additives (and other additives) fed downstream. Ineither case, a generally suitable melt temperature will be about 230 to300° C.

[0045] The pre-compounded composition can be extruded and cut up intomolding compounds such as conventional granules, pellets, etc., bystandard techniques.

[0046] The composition can then be molded in any equipmentconventionally used for thermoplastic compositions, e.g., a Newbury typeinjection molding machine with conventional cylinder temperatures, e.g.,230 to 280° C., and conventional mold temperatures, e.g. 55 to 95° C.

[0047] The following examples illustrate the invention. They are setforth as a further description but are not to be construed as limitingthe invention thereto. All amounts are by weight percent.

EXAMPLES

[0048] All formulations are made by dry-blending of ingredients withexception of BPA-diphosphate, RDP and glass fiber. The blends aresubsequently compounded on a WP 25 mm co-rotating extruder, where RDP orBPA-DP and Glass are fed separately down-stream the extruder.Temperature setting was 50-140-265-260-260-260-260-260-275 C, vacuum 0.2bar and RPM of 300. Molding is done on a Engel 35 tons with temperaturesetting of 245-255-265-265 (from throat to nozzle) and a moldtemperature of 70 C for the PBT-based formulations and 80 C for thePET-based formulations (or otherwise stated). Prior to molding thepellets were pre-dried at 120 C for 4 hrs.

[0049] Materials identified in the tables by abbreviations or tradenames are as follows:

[0050] Poly(butylene terephthalate) with Mw of appr. 80,000 (asexpressed as PS molecular weight)

[0051] (Poly(ethylene terephthalate) with Mw of appr. 60,000 or 45,000(expressed as PS molecular weight).

[0052] RDP Resorcinol diphosphate

[0053] BPA-DP Bisphenol A-diphosphate

[0054] TSAN PTFE/SAN blend of PTFE/SAN=50/50

[0055] X4PIP Tetraxylyl piperazine diphosphoramide

[0056] The flammability of test specimens is evaluated according to thestandard Glow Wire Test (GWT) protocol as described in the Internationalstandard IEC 695-2-1/2. Ratings of 960 GWT indicate test samples withthe best resistance to burning, whereas 850 GWT rating is a lower degreeof resistance to burning if it failed at 960 degrees C.

[0057] The flammability of test specimen is also evaluated according tothe standard UL-94 protocol, vertical burning. Ratings of V0 indicatetest samples with the best resistance to burning, whereas V1 and V2ratings in that order indicate a lessening degree of resistance toburning (V2 with drippings).

[0058] Test specimen are evaluated for Izod Impact in accordance withISO 180. The color of test specimen after oven aging during 500 hours at150 degrees C. were visually inspected.

[0059] Formulations and test results are shown in the table. Amounts arepart by weight. It has been surprisingly found that the right balance ofproperties can be obtained. The following are observations relating tothe results. Formulations based on BPA-DP or X4PIP do not show darkbrown discoloration upon oven aging (500 hrs at 150 C), in contrast toRDP-containing formulations (Reference samples #1, #3 and #4). Sampleswith a PET/PBT ratio<55/45 (Reference samples #1, #2, and #3) do nothave a V0 rating, even not at high amounts of P- and N-compounds.Samples with a ratio of P+N-cpds/Polyester<0.3 for PET/PBT>55/45 show noV0 rating (Reference samples #5, #6 and #7). Reference sample #8 versus#9 shows that an anti-dripping agent is needed for a V0 rating. Sampleswith a ratio of P+N-cpds/Polyester>0.6 for a PET/PBT>55/45 show impactproperties below 25 kJ/m2 (Reference sample #12), in contrast withsamples with a ratio <0.6. Samples with a P-/N-compound ratio <0.8 alsoshow bad impact (Reference sample #5 versus #6, and #11 versus #9). Toobtain a material with good impact also a minimum molecular weight isneeded; sample #14 is added as Reference. #1 #2 #3 #4 #5 #6 #7 #8 #11#12 #14 Ingredients (Ref) (Ref) (Ref) (Ref) (Ref) (Ref) (Ref) (Ref) #9#10 (Ref) (Ref) #13 (Ref) PBT (Mw˜ 44.3 39.8 28 84,000) PET (Mw˜ 15 44.854.8 54.8 54.6 44.8 44.3 49.3 44.3 39.3 44.3 60,000) PET (Mw˜ 44.345,000) RDP 15 13 15 BPA-DP 15 5 10 10 15 15 10 10 15 15 X4PIP 15 Mel.Cyan. 10 15 13 10 10 5 5 10 10 10 15 15 10 10 TSAN 0.5 0.5 0.6 0.2 0.50.5 0.5 0.5 0.5 0.5 GF 30 30 30 30 30 30 30 30 30 30 30 30 30 30Stab/Pigments 0.2 0.2 0.4 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2P + N − 0.56 0.75 0.6 0.56 0.27 0.27 0.27 0.56 0.56 0.41 0.56 0.76 0.560.56 cpds/Polyester P−/N− compound 1.5 1 1 1.5 0.5 2 2 1.5 1.5 1 0.67 11.5 1.5 PET/PBT 0/100 0/100 35/65 100/0 100/0 100/0 100/0 100/0 100/0100/0 100/0 100/0 100/0 Properties IUI (kJ/m2) 44 37 32 32 25 36 38 3330 33 21 21 26 17 UL @ 1.6 mm NC NC V2 V2 V2 V2 V1/V2 V2 V0 V0 V0 V0 V0V0 960 C GWT @ No pass No pass Pass Pass Pass Pass Pass Pass Pass PassPass Pass Pass Pass 1 mm Color after 500 Dark Beige Dark Dark BeigeBeige Beige Beige Beige Beige Beige Beige Beige Beige hrs @ 150 C. BrownBrown Brown

[0060] While preferred embodiments have been shown and described,various modifications and substitutions may be made thereto withoutdeparting from the spirit and scope of the invention. Accordingly, it isto be understood that the present invention has been described by way ofillustration and not limitations.

What is claimed is:
 1. A halogen-free, flame retardant polyestercomposition comprises, based on the total composition, (a) Apoly(ethylene terephthalate) with a molecular weight of at least 50,000or a blend of poly(ethylene terephthalate) with another polyester,taking into account that the ratio poly(ethylene terephthalate)/otherpolyester should be at least 55/45, (b) A combination of at least oneN-containing compound, selected from the group of triazine, guanidine,or (iso)cyanurate compounds, and at least one P-containing compound,selected from the group of BPA-diphosphates or phosphoramides with theproviso that the ratio of the total amount of P- and N-containingcompounds over the total polyester amount should be between 0.3 and 0.6and the ratio of the P-containing compound over the N-containingcompound should be higher than 0.8, (c) An anti-dripping agent in anamount of 0.01-2 weight percent of the total composition, (d) Areinforcing filler in an amount of 0-40 weight percent of the totalcomposition.
 2. The composition of claim 1, further comprising up toabout 40 weight percent of glass fiber.
 3. The composition of claim 1,wherein the other polyester resin is derived from an aliphatic orcycloaliphatic diol, or mixtures thereof, containing from 3 to about 10carbon atoms and at least one aromatic dicarboxylic acid.
 4. Thecomposition of claim 1, wherein the other polyester has repeating unitsof the following general formula:

wherein n is an integer of from 3 to 6, and R is a C6-C20 aryl radicalcomprising a decarboxylated residue derived from an aromaticdicarboxylic acid.
 5. The composition of claim 1, wherein the ratio ofthe total amount of P- and N-containing compounds over the polyester isbetween 0.35 and 0.58.
 6. The composition of claim 1, wherein the ratioof the P-containing compound over the N-containing compound is between0.8 and 2.5
 7. The composition of claim 1, wherein the ratio of theP-containing compound over the N-containing compound is higher than 1.08. The composition of claim 7, wherein the ratio of the P-containingcompound over the N-containing compound is between 1.0 and 3.0, andpreferably between 1.2 and 2.5
 9. The composition of claim 1, whereinthe N-containing compound is a melamine derivative as melaminecyanurate, melamine pyrophosphate or melamine polyphosphate.
 10. Thecomposition of claim 1, wherein the phosphorus-based compound is abisphenolic diphosphate as bisphenol A-diphosphate.
 11. The compositionof claim 1, wherein the phosphorus-based compound is a phosphoramidecompound as tetraxylyl piperazine diphosphoramide.
 12. The compositionof claim 1, wherein the anti-dripping agent is present in an amount of0.02-2 weight percent of the total composition, and preferably in anamount between 0.05 and 1 weight percent.
 13. The composition of claim1, wherein the anti-dripping agent is poly(tetrafluoroethylene).
 14. Thecomposition of claim 1, further comprising up to about 60 weight percentof alumina, amorphous silica, anhydrous aluminum silicates, mica,feldspar, clays, talc, glass flake, glass fibers, glass microspheres,wollastonite, metal oxides such as titanium dioxide, zinc oxide, groundquartz, and mixtures thereof.